Propulsion device for swimmers



May 12, 1970 B. ERlKsEN 3,510,894

PROPULSION DEVICE FOR SWIMMERS Fla Filed Jan. 14. 1969 Q EL INVENTOR.BYRON ERIKSEN Attorneys United States Patent O ABSTRACT F THE DISCLOSUREA device for assisting a swimmer to travel through the water comprises aiioat and pair of paddles secured to the iioat and projecting in opposedrelation therefrom. The device is manufactured from a foamed plasticmaterial and has a high density outer skin and a low density innerstructure.

This invention relates in general to water propulsion devices for aidingswimmers in traveling through water, and pertains more particularly to acombined oat and paddle device having an outer skin of relatively denseplastic material with an interior structure comprising a foam plastic oflesser density than the outer skin.

While devices of this general type have been known to the prior art forsome time, the present invention provides for the iirst time in a uniqueand novel manner a float and paddle device which affords more strength,results in substantially greater safety in congested areas, and can bemanufactured simply 'and inexpensively by molding techniques.

A typical device known to the prior art is shown in U.S. Pat. 1,509,551issued Sept. 23, 1924 to Andrew Gibson. The device as shown in thisprior art patent essentially comprises a shaft to the central portion ofwhich is encompassingly attached a canvas bag having an inflatablebladder mounted therein. Paddle blades are attached to the end portionsof the shaft by means of bolts. Obviously, the entire strength of thisdevice is obtained from the central shaft while the canvas bag andbladder combination do not materially add to the strength of the paddledevice. The construction is cumbersome, complicated and dangerous whenused in crowded bathing areas.

It is accordingly yan object of the present invention to provide animproved water propulsion device for swimmers embodying apparatus forreducing and substantially eliminating safety hazards to swimmers andbathers in the immediate vicinity in which the device is employed.

Another object of the present invention is to provide a device whichwill 'assist in propelling the body of a swimmer through water at agreater rate of speed than can be obtained by a swimmer without the aidof the device.

Another object of this invention is to provide a device which will serveas a safety iioat as well `as a paddle apparatus for eflicientlyassisting a swimmer to traverse a considerable distance in water withease. In this regard, it is an aim of the invention to provide a deviceof foamed plastic material in which the entire structure lends buoyancyto the swimmer.

A further object of the present invention is to provide a propulsiondevice for swimmers which has considerably more strength on a densitybasis than devices heretofore known to the prior art.

Yet another object is to provide a propulsion device of the foregoingcharacter that will last indefinitely because the plastic material fromwhich it is made does not deteriorate.

A still further object of the invention is to provide a water propulsiondevice for swimmers which can be 3,510,894 Patented May l2, 1970manufactured in a single unit or economically from but a few parts.

Other advantages, features and objects of the invention will become moreapparent with the teachings of the principles thereof in connection withthe disclosure of the preferred embodiments thereof in thespecification, claims and drawings.

Brief description of the drawings FIG. 1 is a front elevational view,shown partially in cross section, of the device constructed inaccordance with the principles of the present invention;

FIG. 2 is a plan View of the device of the present invention;

FIG. 3 is a sectional view taken in the direction of line 3 3 of FIG. 2;and

FIG. 4 is a fragmentary sectional view of a modied arrangement of thestructure shown in FIG. 1.

IDescription of the drawing Referring to the drawing, and particularlyto FIGS. 1 and 2, the water propulsion device of my invention iscomprised of a central tear-shaped portion 10 having a major axis 11 anda minor axis 12 passing at right angles through the sides of the centralportion 10 and intersecting the major axis 11 at right angles as shownin FIG. 2. As viewed in FIG. l, the major axis 11 resides in a Verticalplane 11a and appears as a point where the minor axis intersects orpasses through this -vertical plane. The central portion 10, whenconstructed in the tear-shape as shown, constitutes a streamlined floatelement which can be manipulated by a swimmer and yet will offer aminimum of resistance when caused to travel over the surface of water.

At locations 13 and 14, and in a vertical plane containing the minoraxis 12, shaft portions 15 and 16 are connected to the central portion10. As will be discussed in detail hereinbelow, the shaft portions 15and 16 may be integral with the central portion 10 or suitably bondedthereto.

As shown in FIG. l and 2 the shaft portions 15 and 16 extend outwardlyat each side from the central portion 10, the shaft portions incliningslightly upwardly as illustrated in FIG. 1. The outer ends 17 and 18 ofthe shaft portions 15 and 16 are equipped `with paddle blades 19 and 20.The paddles 19 and 20 are in the form of relatively thin iiat blades andlie somewhat to either side of a vertical plane 12a (FIG. 3) containingthe minor axis 12 as mentioned above 'and thus reside in a planetransverse to the longitudinal axis 11 of the central portion 10 (whichplane 12a is of course perpendicular to the plane 11a), being positionedequidistant from the central por tion, as shown. The shaft portions 15and 16 are of such cross sectional dimension and length as will permiteasy mnaual grasping so as to enable a swimmer to hold the shaftportions 15 and 16 in each hand respectively durmg use.

In the use of the water propulsion device of my invention the centralportion 10 is placed upon the water and the shaft portions 15 and 16 arepermitted to lie above the surface of the water with the paddle blades19 and 20 presenting a vertical surface adapted to be alternately dippedinto the water for propulsion 0f the swimmers body. The central portion10 is caused to rock about the longitudinal axis 11 (that is the plane11a shifts angularly to either side of the vertical position that hasbeen illustrated in FIG. l) and also to be oscillated forwardly andrearwardly in a generally horizontally plane as the swimmer manuallyactuates the paddle members 19 and 20.

Thus, one hand of the swimmer causes the shaft 16 to be dipped into thesurface of the water and to be pulled rearwardly to advance the swimmerand the central portion and automatically causing the other shaftportion to raise the opposed paddle blade 19 and to move it forwardlywith respect to the central portion 10. After the second named paddleblade 19 has been moved to its forwardmost position, it is then loweredso as to lie beneath the surface of the water and is subsequently drawnrearwardly to cause forward propulsion of the central portion 10 and theswimmers body.

It will be noted that the generally tear-shaped character of the centralportion 10 is such as to present a streamlined surface to the waterirrespective of the rocking movement and to offer a minimum ofresistance to the water as the swimmer and the apparatus progresstherethrough.

If the swimmer becomes tired and desires to rest before continuing, hemay pull the central portion 10 beneath his torso and hold the apparatusin position so as to support his body until he is again ready toproceed.

The apparatus of the present invention eiciently simulates a pair ofpaddles or oars which are alternately dipped and pulled through thewater with similar motion to that required when rowing a boat. However,since the resistance of a boat hull is not present and since the centralportion 10 has a streamlined configuration as previously noted, aminimum of resistance is offered by the apparatus. For this reason, aswimmer utilizing this apparatus can easily propel himself through thewater more rapidly and efficiently than with a rowboat utilizing oars ofcomparable structure.

As previously indicated, the apparatus of the present invention isconstructed in a unique and novel manner affording additional strengthwhile maintaining a high degree of buoyance and providing for moresafety in congested areas. Essentially, the apparatus is constructed ofa molded plastic having an outer skin of relatively dense material and arelatively low density inner structure. Characteristically, therefore,the structure of the present invention comprises a cellular core and anintegral solid skin which structure may be obtained by one of severalmethods which will be described in detail hereinbelow.

It can be shown that a foamed or cellular structure is at least fourtimes as rigid as its solid counterpart of the same weight.

By way of demonstration, it will be appreciated that the deflectionformula for a cantilever beam states that the deection y, is equal toPL3/3EI where P is the load;

L is the beam length;

E is the modulus of elasticity of the material and I is thecross-sectional moment of inertia, which is equal to where b and lz arethe width and thickness of the beam, respectively.

If the load, length and width are kept constant, the deection formulasimplifies to K/Eh3 (1) If the material is now foamed to one-half itsoriginal specific gravity and the weight held constant, the thicknesswill double and the modulus, being approximately linear with density,will increase by one-half.

Substituting then in Equation 1 Ef=1/2Es hf=2hs where the subscripts fand s refer to foam and solid,

yields:

yf: YS/f It will thus be seen that a foamed structure will be four timesas rigid as its solid counterpart of the same weight.

The manufacture of foamed structures yields another advantage which addsto the strength to the'ultimate product in that a solid skin formedduring the molding process which encloses the molded material and whichskin is typically 0.040 inch thick in a one quarter inch section.

An extruder, and accumulator, a hydraulic press, and a mold are theequipment needed to mold structural foam products. The extruder feedsand melts the plastic raw material. A blowing agent is introduced intothe plastic melt while it is still in the extruder, at about the midwaypoint.

The accumulator is divided into two chambers by a piston, the topside ofwhich is pressurized to two thousand to three thousand p.s.i. Theplastic-gas mixture pumped by the extruder works against this pressureand therefore remains in a compressed and unfoamed state. When theaccumulator has been filled with the desired amount of material, a valveclosing off access to the mold is opened and the plastic-gas mixture israpidly forced out of the accumulator and into the mold. The valve thencloses and the filling cycle repeats. The two forces involved in fillingthe mold with plastic are the direct pressure exerted by the accumulatorand the expansion of the gas as it leaves the high pressure accumulatorand enters the low pressure mold. The force required to keep the moldclosed is supplied by the hydraulic press and is in the range of 200-300p.s.i. times the projected area of the part to be molded. Thecharacteristic structure of a cellular core and integral solid skin isformed during the mold fill. As the material ows through the mold, thesurface cells are ruptured by the shearing action of the materialflowing against the mold surface. This produces a solid skin, asmentioned above, that is typically 0.040 inch thick in a one-quarterinch thick section. After the mold has been filled, the part is cooledsufficiently and then ejected.

The above-described device used for the manufacture of my paddle deviceis well known to those skilled in the art and need therefore not bedescribed herein with additional particularity.

In FIG. 3, the high density skin has been designated by the numeral 21at one side and by the numeral 22 at the other. It will be appreciatedthat the skin 21, 22 becomes increasingly important where the thicknessis less. Hence, the presence of a strengthening skin covering thecentral portion is not nearly as important as in the region representedin FIG. 3.

In accordance with the principles of my invention, other methods ofmanufacture may be employed. For example, the device may be molded intwo halves represented by portions lying on either side of the minoraxis 12 denoted in FIG. 2 or 3. In such a situation, two hollow shellswould be molded, the shells corresponding to the skin portions 21 and22, having a typical wall-thickness of 1/s or so. The hollow shellswould then be joined at the plane 12a, which contains the minor axis 12,by means of a suitable glue or bonding agent and the interior of thedevice then filled with a self-foaming plastic such as polystyrene beadsor other suitable plastic foam material. The self-foaming plastic thusinjected into the hollow paddle device, when expanded by heat, resultsin positional oatation under all circumstances. For example, a puncturein the outer shell would not be harmful since the interior is filledentirely with the self-foaming plastic providing for positionaloatation. The same holds true when the high density skin conditionrepresented by the numeral 21, 22 in FIG. 3 prevails, because theexpanded cellular interior does not permit the water to enter due to theblockage by the cell walls.

It will, therefore, be appreciated that with the foregoing methods ofmanufacture the structural advantages of a foamed or cellular structurewill be maintained.

It may also be desirable to manufacture the device of the presentinvention in several constituent parts. For example, as illustrated inFIG. 4, it is feasible to manufacture the central portion as a separateunit, which has been designated 110, and to also manufacture the shaftportions and 16 with the paddle blades 19, 20 thereon as separate units.In this particular instance the central portion 110 is provided with arecess 125 of suitable diameter and shape while the depicted shaftportion 115 is provided with a suitable stub portion 126 which will fitinto the recess 125. The shaft portion 115 may then be suitably bondedto the central portion 110.

The procedure pictorially outlined in FIG. 4 may have certain advantagesin that it reduces the size of the required molds and the same mold maybe used for each of the shaft portions, thus reducing the total capitalinvestment. Stated somewhat differently, one mold would be made for thecentral portion 110 and a second mold for the shaft portion 115 and theblade (not shown in FIG. 4) which would be integral therewith. lSincethe shaft portion 115 (and its blade) would be duplicated for the leftSide in FIG. 4, just one mold would be required for the combined shaftand blade and one mold for the central portion 110. Such molds, quiteobviously, would be simpler than the single mold required for making theone-piece device of FIGS. 1 and 2. Furthermore, should breakagenecessitate, a shaft and blade could be replaced When utilizing thearrangement of FIG. 4.

It will, of course, be appreciated that in the latter described methodof manufacture I may employ either of the above described moldingtechniques, that is, each of the parts may be molded integrally or inhalves where the shells are joined and lled with a self-foaming plastic.

I claim:

1. A device for assisting a swimmer to travel through the Water whichincludes an elongated central portion having major and minor axes, apair of shaft portions projecting in generally opposite directions fromsaid central portion, said shaft portions projecting at right angles tosaid major axis and in a plane containing said minor axis, said planebeing perpendicular to said major axis, and a blade portion integrallysupported at the free end of each of said shaft portions, all of saidportions being comprised of a foamed plastic material consistingsubstantially the entire device.

2. A device for assisting a swimmer to travel through the water whichincludes a central tear-shaped portion having major and minor axes, apair of shaft portions projecting in generally opposite directions fromsaid central tear-shaped portion at right angles to said major axis andangularly in a plane containing said minor axis, said plane beingperpendicular to said major axis, and a blade portion supported at thefree end of each of said shaft portions, said portions being comprisedof a foamed plastic material.

References Cited UNITED STATES PATENTS 3,186,011 6/1965 Decker 9-241,509,551 9/1924 Gibson 9-24 1,894,874 1/1933 Kask 9-24 2,941,219 6/1960Irving 9-313 3,052,897 9/ 1962 Martin 9-311 3,337,886 8/1967 Ekstrom9-310 MILTON BUCHLER, Primary Examiner J. E. PITTENGER, AssistantExaminer

